Medical testing system with an illuminating component and automatic shut-off

ABSTRACT

A medical testing system has an instrument for monitoring a characteristic of a patient and an illuminating component for illuminating the instrument. The instrument includes a component for selectively activating and deactivating the illuminating component and a deactivating component for automatically deactivating the illuminating component, after a predetermined period of time has elapsed.

BACKGROUND OF THE INVENTION

[0001] The field of the invention generally relates to a medical testingsystem, and more particularly, to a medical testing system with anilluminating component.

[0002] Heart disease is the leading cause of death in the U.S. Heartdisease is any condition that causes your heart to malfunction. When thewords “heart disease” are used generically, it usually refers tocoronary heart disease which leads to heart attacks and angina,ultimately caused by atherosclerosis. But there are a wide range ofother diseases of the heart such as congestive heart failure, valvularheart disease, diseases of the heart valves, cardiac arrhythmias, i.e.,irregular heartbeats, diseases of the pericardium (sac around theheart), diseases of the myocardium (heart muscle), endocarditis(infection of a heart valve), and congenital heart disease, i.e., birthdefects of the heart. There are a number of tools that are available toa physician to help monitor and diagnose malfunctions of the heart. Theyinclude history and physical examinations, chest x-ray, blood tests,echocardiograms, cardiac catheterizations, electrocardiograms, and EKGstress tests.

[0003] An electrocardiogram (“EKG” or “ECG”) for example records theelectrical activity of the heart at rest. For an EKG measurement,electrodes are usually placed on the arms, legs and chest of a patient.These electrodes are connected by wires to an EKG machine. A twelve leadEKG is typically used which generates twelve different tracings orwaveforms. Each waveform provides a view of the heart from a differentangle. These waveforms are stored in memory and if a monitor is used,the waveforms are displayed. In addition, the waveforms may be recordedon paper by a thermal writer or any other conventional writer. A paperroller is driven by a motor that feeds the paper across a heated printerhead. The physician may view and analyze the waveforms on the paperwhich moves across a work surface of the EKG machine. A physician may beable to determine the location of a heart attack based on the EKG leadinvolved. Then, based on his/her knowledge of anatomy, the physician maybe able to determine which artery is blocked. The EKG gives thephysician information about heart rate and rhythm, heart blood supplysufficiency, heart attack, heart enlargement, inflammation around theheart, drug effects, and electrolytes on the heart.

[0004] An EKG stress test is another commonly used procedure to evaluatecoronary artery disease. It uses a similar EKG machine as describedabove with electrodes appropriately positioned on a patient to measurethe electrical activity of the heart. However, these measurements aretaken when the heart is exercised, i.e., “under stress.” EKG stresstests are useful because exercise can reveal abnormalities that were notdetected during an EKG of the heart at rest. In this procedure, aperson's EKG is initially monitored at rest and then monitored whilewalking on a treadmill or pedaling a bicycle. The exercise is graduallyincreased until a target heart rate is reached. If severe EKG changes,chest pain, severe shortness of breath, blood pressure changes orcardiac arrhythmias occur, then the physician may stop the stress test.The EKG stress test may uncover problems with the heart rhythm or bloodsupply to the heart or may provide valuable planning cardiacrehabilitation after a heart attack or heart surgery.

[0005] An echocardiogram (“echo”) is yet another commonly used procedureto evaluate coronary heart disease. The echo uses an ultrasonic beam toview the heart in motion. In this procedure, an ultrasonic transducer,similar in appearance to a microphone, transmits and receives ultrasonicwaves. The transducer is placed on the chest wall and maneuvered to viewdifferent portions of the heart on a monitor. In order to best view themonitor, stress echo tests are performed with the room lights dimmed andthe sunlight suppressed. The echo is used to evaluate the presence ofseveral abnormalities of the heart including (1) abnormal fluidcollection in the pericardium, (2) valve obstruction or leaks, (3)chamber size, thickness of heart wall, as well as other problems.

[0006] In some instances, the EKG and echo stress test procedures areconducted separately at different locations. There is, however, agrowing trend among hospitals and health care providers to use an EKGstress testing system in conjunction with an echo stress testing systemat the same location. In a typical evaluation at a stress laboratory, apatient would first undergo an EKG stress test. Immediately following,usually within 10 seconds, but before the patient's heart returns tonormal, the patient would quickly move to a resting bed to receive anecho stress test by an echo technician. During this time, the physiciancontinues to evaluate the EKG waveforms which appear on the paper alongthe work surface of the EKG machine. Because an echo stress procedure isusually performed in the darkness, the physician is unable to view,analyze and make appropriate notes on the paper relative to thewaveforms with the signals received from the electrodes. If or when thephysician is able to complete his analysis of the EKG waveforms, he/sheis unable to manipulate the keypads to turn the thermal writer off orcontrol any of the other functions of the EKG machine. In sum, thephysician is severely disadvantaged because of the darkness.

SUMMARY OF THE INVENTION

[0007] In an exemplary embodiment of the invention, a medical testingsystem comprising an instrument for monitoring a characteristic of apatient; and an illuminating component for illuminating the instrument,the instrument including: a component for selectively activating anddeactivating the illuminating component; and a deactivating componentfor automatically deactivating the illuminating component, after apredetermined period of time has elapsed.

[0008] In another exemplary embodiment of the invention, a medicaltesting method comprising the steps of: activating an illuminatingcomponent positioned relative to an instrument for monitoring acharacteristic of a patient, the instrument including a keypad having aplurality of keys; determining if a key on the plurality of keys hasbeen pressed by a user; and automatically deactivating the illuminatingcomponent if a key of the plurality of keys has not been pressed withina predetermined period of time.

[0009] In yet another exemplary embodiment of the invention, a medicaltesting system comprising: an instrument for monitoring the electricalactivity of a patient's heart; an illuminating component forilluminating the instrument; the instrument including: a component forselectively turning the illuminating component on and off; a componentfor automatically turning the illuminating component off, after apredetermined period of time has elapsed.

[0010] In yet another exemplary embodiment of the invention, a computerprogram for performing a method comprising the steps of: activating anilluminating component positioned relative to an instrument formonitoring a characteristic of a patient, the instrument including akeypad having a plurality of keys; determining if a key on the pluralityof keys has been pressed by a user; and automatically deactivating theilluminating component if a key of the plurality of keys has not beenpressed within a predetermined period of time.

[0011] In another exemplary embodiment of the invention, a medicaltesting system comprising: means for monitoring the electrical activityof a patient's heart; means for illuminating the instrument, theinstrument including: means for selectively turning the illuminatingcomponent on and off; and means for automatically turning theilluminating component off, after a predetermined period of time haselapsed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a perspective view of the EKG stress testing systemwhich employs a preferred embodiment of the present invention.

[0013]FIG. 2 is a side view of the EKG stress testing system shown inFIG. 1.

[0014]FIG. 3 is an LED circuit board attached to the bottom of themonitor plate for supporting the monitor shown in FIG. 1.

[0015]FIG. 4 is a cross-sectional view of the LED circuit board alonglines 4-4 shown in FIG. 3.

[0016]FIG. 5 is a block diagram of the components of the EKG stresstesting system shown in FIG. 1.

[0017]FIG. 6 is a flowchart of the program for the implementation forautomatic shut off for the LEDs.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] Referring to FIGS. 1 and 2, there is shown an EKG stress testingsystem 10 which incorporates a preferred embodiment of the presentinvention. System 10 includes instrument 12 for controlling the entireoperation of system 10, including processing function commands and thesignals generated from a plurality of electrodes 14 attached to apatient 16. Each electrode has a corresponding wire of preferably twofeet length. In this embodiment, electrodes 14 are coupled to instrument12 by way of a cardiology acquisition module 18 and central cable 20.Cable 20 (preferably 20 feet) connects acquisition module 18 toinstrument 12 and preferably has a connector with 10-12 pins and lockingtabs to ensure that the user properly connects cable 20 to theappropriate port on an acquisition card (discussed below) in the rear ofinstrument 12 and that cable 20 does not become disconnected duringtesting. The ports in the rear of instrument 12 are accessible through alarge opening which is exposed when a flap down door is opened with atool (not shown). Acquisition module 18 functions to convert the analogsignal generated from electrodes 14 into digital signals for instrument12. This is accomplished by several known components including a digitalto analog converter. Acquisition module 18 also includes protectioncircuitry to protect instrument 12 from receiving high energy jolts froma defibrillator.

[0019] Instrument 12 is mounted in a movable cart 22 for maneuverabilityand for transporting system 10 from one location to another. System 10includes several operator control devices, similar to that used in for apersonal computer, such as keyboard 24, mouse 26 and monitor 28. Thesedevices are coupled or connected to the instrument 12 via conventionalcommunication ports that appear in the rear of a computer (video, PS/2,com1), as discussed above. In the present preferred embodiment, keyboard24 and mouse 26 are conventional components which can be purchased offthe shelf. Monitor 28 may also be purchased off the shelf. The presentlypreferred embodiment includes particular component circuitry to isolatea monitor's high voltage requirements from a patient to satisfy UL andother power limitation requirements. The isolation circuitry will bediscussed in more detail below.

[0020] Monitor 28 is supported by plate 30. Neck 32 is attachedunderneath to plate 30 and to the rear of instrument 12. Several screwsand bolts (six) are used to fasten plate 30 to a flat portion of neck 32through corresponding holes in each. The plate 30 and neck 32 functiontogether to support and position monitor 28 above instrument 12. In thepresent preferred embodiment, the height of monitor 28 is fixed relativeto instrument 12. Neck 37 is fastened to a bracket in the rear ofinstrument 12 using nuts which are screwed onto threaded studs on neck32. However, in other embodiments, the neck or other structure may bedesigned for adjustment to enable plate 24 to pivot or rotatehorizontally with respect to instrument 12. In addition, the monitorsupport structure may be adapted to attach to other surfaces such as atable or desk.

[0021] Instrument 12 also includes a dedicated keypad 34 which includesan elastomer pad, key bezel with keys and printed circuit boardcombined. In operation, the keys press on the elastomer which hasconductive pills that press down on the printed circuit board and closea circuit of copper traces on the printed circuit board. Keypad 34refers to these components as combined. The keys of keypad 34 arelocated above the area for keyboard 24. Keypad 34 is used to control thetreadmill and stress test specific functions. For example, there arepreferably keys to control the treadmill such as start/stop, speed andincline keys. There are preferably keys relating to the instructions forthe testing part of the procedure (testing phase settings) such as newtest, pretest, exercise, recovery, test end, hold/pause, and bloodpressure entry. These keys may require personal data input via keyboard24. In addition, there are preferably keys relating to report generationand control such as start and stop thermal writer.

[0022] In the preferred embodiment, there are 22 keys in total, eachwith a backlight to illuminate the key itself. However, any number ofkeys may be employed. One key is used to toggle (turn on and off) thelight source (illuminating component, discussed below) as well as thebacklights for the keys themselves. The remaining 21 keys are keys toenable function of the system 10, as discussed above.

[0023] As will be discussed in more detail below, instrument 12(internally) includes a thermal writer in which a paper roller is drivenby a motor that feeds paper 36 across a heated printer head. Instrument12 also includes work surface 38 over which paper record 36 extends.Waveforms generated from electrodes 14 are recorded and printed on paper36 as it moves through a slot 40 in work surface 38. As paper 36 movesacross work surface 38, paper 36 accumulates in a bin 40 attached tomoveable cart 22, located adjacent instrument 12.

[0024] Referring to FIGS. 2 and 3, system 10 also includes anilluminating component (light source) for illuminating work surface 38and keypad 34. The illuminating component is a circuit board 50 whichincludes a plurality of light emitting diodes (“LED”) 52. Circuit board50 is covered by a clear plastic shield 54 which is bolted to andsupported by the bottom front end of support plate 24. The LEDs 52 arepositioned throughout circuit board 50. Preferably, 15 white LEDs areused. The position of the circuit board 50, together with the number andposition of LEDs on circuit board 50 satisfy the following preferredlight criteria: (1) the light is properly diffused; (2) minimal glare isproduced on paper 36; and (3) the light will last a long time.

[0025] Note that the illuminating component preferably illuminates atleast three areas or “zones.” These zones are work surface 38, keypad34, located just below work surface 38, and keyboard 24. This enablesthe physician to read and analyze the waveforms on paper 36 (on worksurface 38) as well as view and manipulate the keys on keypad 34 andkeyboard 24. System 10 includes cable 56 which is used to provide powerto LED board 50 and LEDs 52 on board 50. Cable 56 has a connector whichis adapted to connect to a port in the interior of instrument 12. It isimportant to note that the illuminating component may be of any type andmay be positioned anywhere so long as the illuminating componentilluminates at least the area in which a physician works on instrument12.

[0026] Referring to FIG. 5, there is shown a block diagram representingthe components of system 10. System 10 includes the customary componentsof a computer such as a master control or motherboard 60, a CDRead/Write drive 62, hard drive 64 and floppy drive 66. Master control60 is used to control the high level operation of system 10. Mastercontrol 60 includes the customary components of a computer, such as amicroprocessor (CPU), memory (RAM and ROM), and I/O devices. In thepreferred embodiment, the motherboard includes a 566 MHz Intel Celeronmicroprocessor, 64 MB SDRAM and Windows NT.

[0027] Acquisition card 68 is inserted into a conventional slot onmotherboard 60. Acquisition card 68 is used to provide a port forreceiving cable 20 and additional ports for other peripheral devices(e.g., treadmill wires, automatic blood pressure devices, pulseoximeters). Acquisition module 18 is coupled to acquisition card 68 andelectrodes 14 are coupled to acquisition module 18. In operation,patient 16 carries acquisition module 18 on his/her waist by a belt.Each electrode is attached to patient 16 at different points on his/herbody. For most patients, electrodes 16 are preferably attached with“stick on contacts” that a technician sticks to the patients' shavenskin. In another embodiment, electrodes 14 may be attached to a patientusing suction elements that run off a pump. The instrument 12 preferablyincludes a pump so the user has the option to choose either embodiment.In either embodiment, electrodes 14 are placed on the body in thetraditional 12-lead electrode placement, which is a specific patternacross the chest and on all 4 limbs. Importantly, electrodes 14 generateanalog signals which are converted by acquisition module 18 into digitalsignals for acquisition card 68.

[0028] As briefly indicated above, a conventional keyboard 24 and mouse26 are connected to motherboard 60 at the appropriate conventionalcommunication ports. In addition, monitor 28 is connected to aconventional video port on motherboard 60. Instrument 12 includes apower management circuit board 70 for providing power to many of thecomponents in instrument 12, including monitor 28. Also brieflydiscussed above, when designing and using medical equipment, it isimportant to isolate the power from the patient, particularly power athigh levels, to prevent injury to the patient in all circumstances. In atypical medical environment, a special monitor with protection circuitrywould be required to satisfy this function. In the present preferredembodiment, however, instrument 12 utilizes a separate protection deviceor isolation transformer 22 to isolate the power supplied to the monitorfrom patient 16. Thus, one may use any off the shelf monitor for thissystem. In practice, monitor 28 is used to display many characteristicsof the patient and of the procedure including the EKG instrumentsettings, the treadmill settings, e.g., grade, speed, blood pressureentered, number of leads, etc.

[0029] Power management board 70 is also coupled to motherboard 60,keypad 34, scan or thermal writer 74, CD Read/Write drive 62, hard drive64, floppy drive 66, the under the monitor lights or circuit board 50(illuminating component). (The scan writer includes a print head, amotor, paper roller and other components necessary for the operation ofthe scan writer). Power management board 70 has two portions 70A, 70B,which in the preferred embodiment, are integrated on the same board.However, these portions may be two separate boards.

[0030] Portion 70A is used to receive electricity from a wall socket viaplug 76. Filter 78 is used to filter transient AC signals from the wall.Power is received and processed by portion 70A and fed to power supply80. Power supply 80 is preferably two separate conventional medicalgrade power supplies. However, one would suffice. Power supply 80 isused to convert the power signal from the wall into appropriate DCsignals for portion 70B of power management board 70. Portion 70B isused to supply such DC voltage signals to many of the components as seenin FIG. 5. Note that keypad 34 is shown connected to motherboard 60.Motherboard 60 provides a 5 volt supply to keypad 34 which is usuallyinsufficient to independently power the 22 LEDs that are used tobacklight each of the 22 LEDs on keypad 34. Therefore, keypad 34 is alsocoupled to power management 70 to receive adequate voltage (12 volts) toprovide adequate current to drive the LEDs.

[0031] The circuit board of keypad 34 includes memory, a microcontrollerunit and software to control the functions associated with the keys. Themicrocontroller may be of any type but preferably is a Cypresssemiconductor (No. CY7C63101A-SC). There are preferably 22 keys intotal. Twenty (21) are keys associated with the functions of the EKGinstrument 12 or the treadmill (“function keys”) and one key isassociated with the lights (“light key”). If a user presses a functionkey, the software senses, interprets and decodes the signal as aparticular command, and sends the command to motherboard 60 to implementthe command. If a user presses the key to turn on the thermal printer,for example, the software interprets this signal and sends a command tomotherboard 60. Motherboard 60 thereafter transmits a signal to powermanagement board 70 to provide power to scan writer 74. (Specifically, amosfet transistor on management board 70 receives the signal frommotherboard 60 and turns on power to scan writer 74.) Note the ON/OFFswitch 80 activates the entire system 10.

[0032] A similar operation for execution occurs for all of the functionkeys. However, the operation of the light key is different. Theoperation is discussed in more detail below with reference to FIG. 6. Inbrief, however, the lights will toggle, i.e, turn on and off, inresponse to the depression of the light key. If the lights are off andthe light key is pressed for example, the software senses this signaland sends a command directly to power management board 70 to turn alllights on, including the 15 LEDs under the monitor and the 22 backlightsLEDs for each key. Note that in the preferred embodiment, themicroprocessor on motherboard 60 is isolated or unaware of the operationof the lights.

[0033] The software on board of the keypad 34 also has another featurerelating to the lights. This feature is known as automatic light shutoff. If the lights remain on for a predetermined period of time withoutany activity from the user, the software will automatically turn thelights off. The predetermined period is preferably set to an hour butany desired length may be set. This automatic shut off feature improvesor increases the life of all LEDs. (light intensity of LED's graduallyto dim over time.) The operation of the software with respect to thelights is discussed below.

[0034] Referring to FIG. 6, there is shown a flowchart for the softwarefor the keypad 34 illustrating the execution steps of the method forimplementing automatic light shut-off. As a first step 100, a user flipsa switch and turns on the entire system 10. For purposes of theflowchart, the lights are presumed to be off for the initial settingsstatus.

[0035] Now, execution proceeds to step 102 wherein the keys of thekeypad 34 are scanned for a signal associated with a key depression. Thescanning is performed by a matrix configuration. (Keypad 34 has 22 keys,where 21 are in a 3 by 8 matrix. Note that the light key, i.e., the22^(nd) key is routed directly into an input/output line on themicrocontroller unit for light control. The 3 columns are outputs fromthe microcontroller on keypad 34, and the 8 rows are inputs to themicrocontroller. During non-scanning, the 3 columns are all sitting atlogic high, and the 8 rows all have internal pull-up resistors that makethose lines logic high, when the line is not being driven by a keypress. During scanning, a column is set to logic low, and the 8 rows arechecked to determine if any of those rows are set to a logic low at thattime. If one row is detected, then it is known the key that isresponsible for passing the logic low from that column to that row. Thescan is continued for all 3 columns.) As long as the system 10 isactivated, scanning is performed continually.

[0036] Execution then proceeds to decision box 104, wherein it isdetermined whether a user has pressed a key on keypad 34. If a key hasnot been pressed, then execution proceeds to decision box 106 wherein itis determined if the timer has reached 60 minutes. If 60 has beenreached, then execution proceeds to boxes 108 and 110 wherein the lightsare turned off and the timer is stopped. Then execution returns to box102 wherein scanning continues. If the timer has not reached 60 minutes,execution returns to box 102 again. Because the presumption is thelights are not activated or on for the initial configuration, thesoftware returns to scanning regardless of whether the timer isactivated or has reached 60 minutes. Note that the timer function ispreferably performed by a sub-routine of the software (on keypad 34)which is activated or updated by a hardware generated interrupt serviceroutine on the microcontroller. However, the timer function may beachieved through a hardware timer.

[0037] Returning to decision box 104, wherein it is determined if a keyon keypad 34 has been pressed. If the answer is YES, then executionproceeds to decision box 112, wherein the software determines if the keypressed or activated is the light key. If the answer is NO, theexecution proceeds to box 114, wherein the software determines that thekey activated is a function key and interprets and transmits theappropriate code or instruction to master control or motherboard 60 toimplement the instruction for that function key. Following thetransmission, execution proceeds to box 116 wherein the timer is reset.Execution then returns to scanning in box 102.

[0038] Now, if the answer to decision box 112 is YES, i.e., a user haspressed the light key, then execution proceeds to decision box 118,wherein the software determines if the lights are already on (all LEDs).If the answer is a YES, execution proceeds to boxes 120 and 122 whereinthe lights are turned off (all 37 LEDs) and the timer is stopped.Following this, execution returns to scanning in box 102. If the answerto decision box 118 is NO, then execution proceeds to box 124 whereinthe lights under the monitor (LEDs) and the backlights for the keys areturned on or activated. Following box 124, execution proceeds to box 126wherein the timer is reset and the timer is started. Execution thenreturns to scanning in box 102. The flowchart described above is thepreferred method of implementing light activation and automaticshut-off. There are, however, many other ways to achieve the same goals.

[0039] The foregoing description of a preferred embodiment of theinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed and modifications and variationsare possible in light of the above teachings or may be acquired frompractice of the invention. The embodiment was chosen and described inorder to explain the principles of the invention and its practicalapplication to enable one skilled in the art to utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto and theirequivalents.

What is claimed is:
 1. A medical testing system comprising: (a) aninstrument for monitoring a characteristic of a patient; and (b) anilluminating component for illuminating the instrument, the instrumentincluding: (1) a component for selectively activating and deactivatingthe illuminating component; and (2) a deactivating component forautomatically deactivating the illuminating component, after apredetermined period of time has elapsed.
 2. The system of claim 1,wherein the instrument includes a work surface and the illuminatingcomponent illuminates the work surface.
 3. The system of claim 1,wherein the instrument further includes a keypad and the illuminatingcomponent illuminates the keypad.
 4. The system of claim 1, wherein thecomponent for selectively activating and deactivating includes a toggleswitch.
 5. The system of claim 1, wherein the instrument includes akeypad having a plurality of keys, each associated with an instruction.6. The system of claim 5, wherein the instrument includes a determiningcomponent for determining whether a key has been pressed by a user. 7.The system of claim 6, wherein the deactivating component willautomatically deactivate the illuminating component if a key has notbeen pressed by a user for the predetermined period of time.
 8. Amedical testing method comprising the steps of: activating anilluminating component positioned relative to an instrument formonitoring a characteristic of a patient, the instrument including akeypad having a plurality of keys; determining if a key on the pluralityof keys has been pressed by a user; and automatically deactivating theilluminating component if a key of the plurality of keys has not beenpressed within a predetermined period of time.
 9. The method of claim 8,further comprising the step of deactivating the illuminating componentwhen a toggle key has been pressed.
 10. The method of claim 8, whereinthe characteristic is the electrical activity of the heart of thepatient.
 11. The method of claim 8, wherein the determining stepincludes the step of scanning the keypad for sensing if a key has beenpressed by a user.
 12. The method of claim 11, further comprising thestep of starting a timer, after the activating step, for timing thepredetermined period of time.
 13. The method of claim 12, furthercomprising the step of stopping the timer when a key of the plurality ofkeys has been pressed by a user.
 14. The method of claim 13, furthercomprising the step of resetting the timer after the timer has stopped.15. A medical testing system comprising: (a) an instrument formonitoring the electrical activity of a patient's heart; (b) anilluminating component for illuminating the instrument, the instrumentincluding: (1) a component for selectively turning the illuminatingcomponent on and off; and (2) a component for automatically turning theilluminating component off, after a predetermined period of time haselapsed.
 16. The system of claim 15, wherein the illuminating componentincludes at least one LED.
 17. The system of claim 15, wherein theinstrument includes a work surface and wherein the illuminatingcomponent illuminates the work surface.
 18. The system of claim 15,further includes a supporting component engaging the instrument forsupporting the illuminating component above the instrument.
 19. Thesystem of claim 17, wherein the instrument includes a keypad and whereinthe illuminating component illuminates the keypad.
 20. The system ofclaim 17, wherein the instrument further includes a printing componentfor printing on a medium a graphical waveform representing theelectrical activity of the heart.
 21. The system of claim 20, whereinthe illuminating component illuminates the medium as it moves along thework surface.
 22. A computer program for performing a method comprisingthe steps of: activating an illuminating component positioned relativeto an instrument for monitoring a characteristic of a patient, theinstrument including a keypad having a plurality of keys; determining ifa key on the plurality of keys has been pressed by a user; andautomatically deactivating the illuminating component if a key of theplurality of keys has not been pressed within a predetermined period oftime.
 23. The computer program of claim 22, wherein the predeterminedperiod of time is 60 minutes.
 24. A medical testing system comprising:(a) means for monitoring the electrical activity of a patient's heart;(b) means for illuminating the instrument; the instrument including: (1)means for selectively turning the illuminating component on and off; (2)means for automatically turning the illuminating component off, after apredetermined period of time has elapsed.